URL:Mal help

avast! antivirus is continuously popping up a notification stating that they are blocking a URL:Mal and this is happening every 4 seconds and i myself do not know how to stop this because i have personaly never been very good at handling viruses etc here is what the notification is stating:
avast! Web Shield has blocked a harmful webpage or file.

Object: http://…/spark.bin?rnd= (number varies every new notification)
infection: URL:Mal
Process: C:\Windows\SysWOW64\rundll32.exe

and that is all it has to say i need help as i do not know if this is effecting my computer?

thank you…

Please attach your logs. (MBAM, OTL and aswMBR…!!)
Instructions: http://forum.avast.com/index.php?topic=53253.0